Electronic musical instrument

Abstract

In an electronic musical instrument which generates a musical waveform by calculating the waveform amplitude value at each sample point through Fourier synthesis, there is provided a musical waveform generator for caculating and synthesizing a temporally varying musical waveform at a plurality of sample points, memory circuits for storing two kinds of musical waveforms obtained by the musical waveform generator one after the other and an interpolation circuit for interpolating the two musical waveforms at time intervals shorter than the time intervals used in the musical waveform generator.

What is claimed is: 
     
       1. An electronic musical instrument of the type that forms a musical waveform by calculating the waveform amplitude value at each sample point thereof through Fourier synthesis, comprising: a musical waveform generator for calculating and synthesizing a temporally varying musical waveform at a plurality of representative points of time;   a memory circuit for temporally storing only two musical waveform data which are calculated and synthesized by the musical waveform generator one after the ohter at successive points of time; and   an interpolation circuit for reading out the two musical waveform data from the memory circuit and calculating a plurality of waveform interpolation values corresponding to points on a time axis which are of shorter time intervals than the time intervals of the plurality of representative points of time;   wherein the musical waveform is effectively varied temporally with a small amount of waveform synthesis calculation per unit time.   
     
     
       2. An electronic musical instrument according to claim 1, which the interpolation circuit includes a weight setting circuit for setting a weight function for the two musical waveform data, a temporal variation circuit for temporally varying the weight function and an interpolation calculating circuit for calculating an interpolation value on the basis of the two musical waveform data and the weight function, and wherein the state of temporal variation of the waveform interpolating calculation can be controlled arbitrarily. 
     
     
       3. An electronic musical instrument according to claim 1, wherein the interpolation circuit includes a difference value setting circuit for obtaining a difference value between the two musical waveform data, an incremental value setting circuit for obtaining incremental value data by binary-shifting the difference value and an interpolation calculating circuit for calculating an interpolation value on the basis of the two musical waveform data and the incremental value data, and wherein the state of temporal variation of the waveform interpolating calculation can be controlled exponentially.